At least 2 weeks after the completion of MARAM chemotherapy, patients receive OCTADD chemotherapy comprising oral dexamethasone three times a day on days 1-21; oral thioguanine daily on days 1-28 and 36-49; vincristine IV on days 2, 8, 16, and 22; daunorubicin IV over 60 minutes on days 1, 8, 15, and 22; cytarabine IV on days 2-5, 9-12, 16-19, 23-26, 37-40, and 45-48; cytarabine IT on days 1 and 15; and cyclophosphamide IV over 1 hour on days 36 and 49. Patients receive prednisolone IT in combination with any dose of intrathecal methotrexate.